Electric pressing irons, and in particular spray irons, steam irons, and dry irons, have been used for many years to press clothing and textiles. In prior art irons delivery of continuous steam flow or a burst of instant extra steam is provided through the soleplate to enhance the effectiveness of the pressing operation. In addition, it is well known in the prior art for pressing irons to be controlled to operate at various temperature levels so that different types of fabrics can be ironed most effectively without damaging them. It is well known that ironing efficiency varies directly with temperature so that it is desirable to iron a particular fabric at the highest temperature to which it can be subjected for a reasonable time without scorching.
A number of problems, however, still exist with household pressing irons, not the least of which are related to safety. At times a person using an iron on a piece of clothing can become distracted, stop moving the heated iron, and scorch the fabric, thereby ruining the article of clothing. Unattended irons which are left switched on are a safety hazard. Children often reach for or pick up hot unattended irons and burn themselves.
It should be appreciated, however, that the length of time for which an iron can be left unattended with its soleplate in contact with a piece of clothing or the like is considerably shorter than the amount of time an iron can be left unattended when the soleplate is in a raised position and the iron is supported on its heel rest.
Other problems encountered with prior irons are related to the accuracy of soleplate temperature control which can be achieved. Temperature stability is very important because many modern synthetic materials will be damaged at much lower temperatures than wool or cotton. It is desirable to be able to operate the iron as close as possible to the maximum temperature which such synthetics may safely withstand without damage, but which efficiently irons the synthetic material. It may be appreciated that conventional bimetallic thermostatic controls used in irons are often less than satisfactory for this purpose. The operator must set the bimetal thermostat at a considerably reduced temperature from the maximum at which the iron can be safely operated due to the fact that the soleplate temperature has a tendency to oscillate between a relatively low temperature when the iron heating element is switched on and at a relatively high temperature when the iron heating element is switched off. The temperature oscillations are sometimes described as scallops due to the scallop-shaped curve they define when graphed against time. Such oscillations typically have a magnitude of plus or minus ten degrees Centigrade, although some prior irons using bimetal thermostat controls have oscillations as small as plus or minus five degrees Centigrade.
Another problem with prior irons is that the operator of an iron is often unable to determine when the iron soleplate has reached the operating temperature for which the iron thermostat is set. It is well known for people to test crudely the temperature of the iron soleplate by lightly and quickly touching it with a finger or dropping droplets of water onto the soleplate to determine how rapidly they vaporize. This, of course, is only practical when dry ironing is done due to the fact that the soleplate temperature is often lower when steam ironing. Particularly at the lower temperatures at which synthetic fabrics are commonly ironed, it is often difficult to tell whether or not the soleplate has reached ironing temperature.
Another problem often faced by users of prior art steam irons and in particular steam irons with an instant extra steam feature of the type disclosed in U.S. Pat. No. 4,398,364 to Augustine et al. for STEAM IRON is that when the iron is being operated with the soleplate at a relatively low temperature in order to iron certain synthetic fabrics, the normal large temperature swings in the soleplate caused by the use of a bimetal thermostat control often will allow the soleplate to drop below the steaming temperature of the iron, thereby inhibiting steam generation. The problem is made worse if, at the moment the user of the iron actuates the instant extra steam feature causing an additional charge of water to enter the steaming or flash chamber, the soleplate happens to be at the bottom of one of its temperature swings, because relatively small amounts of steam will be emitted from the steam vents in the soleplate and volumes of water will be ejected rather than having all the water completely converted to steam as intended. This situation produces a condition typically known as spitting.
What is needed, then, is a pressing iron which interrupts electric current to its electric heating element when the soleplate is resting on a surface and the iron is not moving for a period of time. The iron should also have the ability to interrupt electric power to its own heating element when it has been left in the heel rest position for a longer period of time. The iron should have accurate temperature control to permit efficient ironing of synthetics and should provide an external indication to the operator as to when the soleplate is operating at the preselected ironing temperature and when the soleplate is being heated to reach the preselected ironing temperature.